Need help - calculating daily, weekly, and monthly totals based two dates and networkdays

Only bill for week days during billing cycle (i.e. M-F).
More than 3 days = 1 week's rental
More than 3 weeks = 1 Month's Rental

Currently "Days" in column E are calculated using Networkdays function.
Based on entering two dates (Rent start, Rent finished), I need to calculate the number of Months, Weeks, and Days then run a formula to calculate the total value to invoice.

The highlighted cells under columns J,K,L on row 18 are my initial attempts at this calculation. Please Help!!

I've attached the excel sheet.

2 days = 2 days
3 days = 1 week
4 days = 1 week
5 days = 1 week
6 days = 1 week, 1 day
7 days = 1 week, 2 days
8-10 days = 2 weeks
11 days = 2 weeks, 1 day
12 days = 2 weeks, 2 days
13-22 days = 1 Month
23 days = 1 month, 1 day
etc.

Anyone?
I've created a table from 1-365, but there has to be a formula out there.
Thanks!

Were you able to take a look at my response to your question?
Thanks in advance.

You've gone quite a ways over my head here, but I think I'm following you.
I added in the function, and the output is now in J13.
I would guess the next step is to somehow separate these outputs into the appropriate cells within the function code? I'm not real familiar with VBA code, so I'm open to next step suggestions.
Thanks again.

I've got to run into a meeting, will give it a go later in the day.
Thanks again, I'll let you know if I have any questions.

I've updated the function, but have an error.
When I update the work days to show 49 days, the function produces 2 months and 1 day, when it should show 2 months and 1 week. I'm using the table in the "DaysTable" tab as my reference to check the function.
Any thoughts?